- Clinically significant dilated cardiomyopathy, evidence of regional wall motion abnormalities suggestive of prior myocardial infarction, rheumatic mitral valve disease, moderately severe or worsening cardiac valvular disease (> 2+ on a scale of 4), known or suspected congenital heart disease, evidence of right sided volume or pressure overload, history of atrial fibrillation. Patients with PFO, atrial septal defect, or other right-to-left shunt are not excluded unless associated with other abnormalities as above.